Satow was an exceptional linguist, an energetic traveller, a writer of travel guidebooks, a dictionary compiler, a mountaineer, a keen botanist (chiefly with F.V. Dickins) and a major collector of Japanese books and manuscripts on all kinds of subjects before the Japanese themselves began to do so. He also loved classical music and the works of Dante on which his brother-in-law Henry Fanshawe Tozer was an authority. Satow kept a diary for most of his adult life which amounts to 47 mostly handwritten volumes.

As a celebrity, albeit not a major one, he was the subject of a cartoon portrait by Spy in the British Vanity Fair magazine, 23 April 1903.

Ernest Satow is probably best known as the author of the book A Diplomat in Japan (based mainly on his diaries) which describes the years 1862–1869 when Japan was changing from rule by the Tokugawa shogunate to the restoration of Imperial rule. He was recruited by the Foreign Office straight out of university in London. Within a week of his arrival by way of China as a young student interpreter in the British Japan Consular Service, at age 19, the Namamugi Incident (Namamugi Jiken), in which a British merchant was killed on the Tōkaidō, took place on 21 August 1862. Satow was on board one of the British ships which sailed to Kagoshima in August 1863 to obtain the compensation demanded from the Satsuma clan's daimyo, Shimazu Hisamitsu, for the slaying of Charles Lennox Richardson. They were fired on by the Satsuma shore batteries and retaliated, an action that became known in Britain as the Bombardment of Kagoshima.

Satow's rise in the consular service was due at first to his competence and zeal as an interpreter at a time when English was virtually unknown in Japan, the Japanese government still communicated with the West in Dutch and available study aids were exceptionally few. Employed as a consular interpreter alongside Russell Robertson, Satow became a student of Rev. Samuel Robbins Brown, and an associate of Dr. James Curtis Hepburn, two noted pioneers in the study of the Japanese language.[2][3] His Japanese language skills quickly became indispensable in the British Minister Sir Harry Parkes's negotiations with the failing Tokugawa shogunate and the powerful Satsuma and Chōshū clans, and the gathering of intelligence. He was promoted to full Interpreter and then Japanese Secretary to the British legation, and, as early as 1864, he started to write translations and newspaper articles on subjects relating to Japan. In 1869, he went home to England on leave, returning to Japan in 1870.

Satow was one of the founding members at Yokohama, in 1872, of the Asiatic Society of Japan whose purpose was to study the Japanese culture, history and language (i.e. Japanology) in detail. He lectured to the Society on several occasions in the 1870s, and the Transactions of the Asiatic Society contain several of his published papers. The Society is still thriving today.[4]

During his time in Japan, Satow devoted much effort to studying Chinese calligraphy under Kōsai Tanzan 高斎単山 (1818–1890), who gave him the artist's name Seizan 静山 in 1873. An example of Satow's calligraphy, signed as Seizan, was acquired by the British Library in 2004.[5]

Satow served in Siam (1884–1887), during which time he was accorded the rare honour of promotion from the Consular to the Diplomatic service,[6]Uruguay (1889–93) and Morocco (1893–95). (Such promotion was extraordinary because the British Consular and Diplomatic services were segregated until the mid-20th century, and Satow did not come from the aristocratic class to which the Diplomatic Service was restricted.)

In retirement (1906–1929) at Ottery St Mary in Devon, England, he wrote mainly on subjects connected with diplomacy and international law. In Britain, he is less well known than in Japan, where he is recognised as perhaps the most important foreign observer in the Bakumatsu and Meiji periods. He gave the Rede lecture at Cambridge University in 1908 on the career of Count Joseph Alexander Hübner. It was titled An Austrian Diplomat in the Fifties. Satow chose this subject with discretion to avoid censure from the British Foreign Office for discussing his own career.

As the years passed, Satow's understanding and appreciation of the Japanese evolved and deepened. For example, one of his diary entries from the early 1860s asserts that the submissive character of the Japanese will make it easy for foreigners to govern them after the "samurai problem" could be resolved; but in retirement, he wrote: "... looking back now in 1919, it seems perfectly ludicrous that such a notion should have been entertained, even as a joke, for a single moment, by anyone who understood the Japanese spirit."[10]

Satow's extensive diaries and letters (the Satow Papers, PRO 30/33 1-23) are kept at the Public Record Office at Kew, West London in accordance with his last will and testament. His letters to Geoffrey Drage, sometime MP, are held in the Library and Archives of Christ Church, Oxford. Many of his rare Japanese books are now part of the Oriental collection of Cambridge University Library and his collection of Japanese prints are in the British Museum.[11]

Satow was never able, as a diplomat serving in Japan, to marry his Japanese common-law wife, Takeda Kane 武田兼 (1853–1932), by whom he had two sons, Eitaro and Hisayoshi, and a daughter.[5] The Takeda family letters, including many of Satow's to and from his family, have been deposited at the Yokohama Archives of History (formerly the British consulate in Yokohama) at the request of Satow's granddaughters.

A Handbook for Travellers in Central and Northern Japan, by Ernest Mason Satow and A G S [Albert George Sidney] Hawes

A Handbook for Travellers in Central and Northern Japan: Being a guide to Tōkiō, Kiōto, Ōzaka and other cities; the most interesting parts of the main island between Kōbe and Awomori, with ascents of the principal mountains, and descriptions of temples, historical notes and legends with maps and plans. Yokohama: Kelly & Co.; Shanghai: Kelly & Walsh; Hongkong: Kelly & Walsh, 1881.

A Handbook for Travellers in Central and Northern Japan: Being a guide to Tōkiō, Kiōto, Ōzaka, Hakodate, Nagasaki, and other cities; the most interesting parts of the main island; ascents of the principal mountains; descriptions of temples; and historical notes and legends. London: John Murray, 1884.[n 1]

A Guide to Diplomatic Practice by Sir E. Satow, (Longmans, Green & Co. London & New York, 1917). A standard reference work used in many embassies across the world, and described by Sir Harold Nicolson in his book Diplomacy as "The standard work on diplomatic practice," and "admirable."[13] Sixth edition, edited by Sir Ivor Roberts (2009, ISBN 978-0-19-955927-5).

A Diplomat in Japan by Sir E. Satow, first published by Seeley, Service & Co., London, 1921, reprinted in paperback by Tuttle, 2002. (Page numbers are slightly different in the two editions.) ISBN 4-925080-28-8

'British Policy', a series of three untitled articles written by Satow (anonymously) in the Japan Times (ed. Charles Rickerby), dated 16 March, 4 May (? date uncertain) and 19 May 1866 which apparently influenced many Japanese once it was translated and widely distributed under the title Eikoku sakuron (British policy), and probably helped to hasten the Meiji Restoration of 1868. Satow pointed out that the British and other treaties with foreign countries had been made by the Shogun on behalf of Japan, but that the Emperor's existence had not even been mentioned, thus calling into question their validity. Satow accused the Shogun of fraud, and demanded to know who was the 'real head' of Japan and further a revision of the treaties to reflect the political reality. He later admitted in A Diplomat in Japan (p. 155 of the Tuttle reprint edition, p. 159 of the first edition) that writing the articles had been 'altogether contrary to the rules of the service' (i.e. it is inappropriate for a diplomat or consular agent to interfere in the politics of a country in which he/she is serving). [The first and third articles are reproduced on pp. 566–75 of Grace Fox, Britain and Japan 1858–1883, Oxford: Clarendon Press 1969, but the second one has only been located in the Japanese translation. A retranslation from the Japanese back into English has been attempted in I. Ruxton, Bulletin of the Kyūshū Institute of Technology (Humanities, Social Sciences), No. 45, March 1997, pp. 33–41]

Korea and Manchuria between Russia and Japan 1895–1904: the observations of Sir Ernest Satow, British Minister Plenipotentiary to Japan (1895–1900) and China (1900-1906), Selected and edited with a historical introduction, by George Alexander Lensen. – Sophia University in cooperation with Diplomatic Press, 1966 [No ISBN]

On September 1992, BBC Two screened a two-part dramatisation of Satow's life, titled A Diplomat in Japan in the Timewatch documentary strand. Written and directed by Christopher Railing, it starred Alan Parnaby as Satow, Benjamin Whitrow as Sir Harry Parkes, Hitomi Tanabe as Takeda Kane, Ken Teraizumi as Ito Hirobumi, Takeshi Iba as Inoue Kaoru, and Christian Burgess as Charles Wirgman.